Blast furnace stove

ABSTRACT

A blast furnace stove or like air heater is provided in which the main stove wall, i.e., the ring wall, is an integral wall of poured refractory concrete having varying refractory properties to provide a varying degree of heat resistance increasing from the bottom to the top of the wall. The dome portion of the stove can conveniently be constructed of firebrick so that the stove shell or wall provides proper heat resistance in accordance with the temperature to which the various zones of the stove, and the checkers contained therein, are subjected. An inner liner of joined steel plates are used as a form for pouring the refractory concrete during construction of the refractory wall and plates can be retained in place if desired. An alloy steel structure supports the checker network within the stove and, as desired, heat exchange tubing or the like is provided in close proximity to the steel structure for cooling the structure below a temperature at which failure in the steel may occur. The heat exchange tubing is covered by a steel shield which provides a dead air space for further protection of the support structure. Heat exchange tubes are also embedded in the masonry work covering a steel bottom plate of the stove and heat exchange fluid such as water is circulated through the heat exchange tubes for cooling the bottom plate.

United States Patent [72] Inventor John E. Allen 606 Timber Lane, Lake Forest, 111. 60045 [21] Appl. No. 13,329 [22] Filed Feb. 24, 1970 [45] Patented Dec. 7, 1971 [54] BLAST FURNACE STOVE 20 Claims, 9 Drawing Figs.

[52] 11.8. CI 263/19 [51 Int. Cl. F231 15/02 [50] Field of Search 263/19, 51

[56] References Cited UNITED STATES PATENTS 2,187,191 1/1940 Youngiove 263/19 2,420,373 5/1947 Hogberg... 263/19 3,122,359 2/1964 MacDonald. 263/19 3,528,647 9/1970 Hyde 263/19 Primary Examiner-Edward G. Favors Attorney-Hofgren, Wegner, Allen, Stellman & McCord ABSTRACT: A blast furnace stove or like air heater is provided in which the main stove wall, i.e., the ring wall, is an integral wall of poured refractory concrete having varying refractory properties to provide a varying degree of heat resistance increasing from the bottom to the top of the wall. The dome portion of the stove can conveniently be constructed of firebrick so that the stove shell or wall provides proper heat resistance in accordance with the temperature to which the various zones of the stove, and the checkers contained therein, are subjected. An inner liner ofjoined steel plates are used as a form for pouring the refractory concrete during construction of the refractory wall and plates can be retained in place if desired. An alloy steel structure supports the checker network within the stove and, as desired, heat exchange tubing or the like is provided in close proximity to the steel structure for cooling the structure below a temperature at which failure in the steel may occur. The heat exchange tubing is covered by a steel shield which provides a dead air space for further protection of the support structure. Heat exchange tubes are also embedded in the masonry work covering a steel bottom plate of the stove and heat exchange fluid such as water is circulated through the heat exchange tubes for cooling the bottom plate.

PATENTED [15c 7I97| 3.625494 sum 1 OF A PATENTED DEC 7 I971 SHEET 2 [1F 4 BLAST FURNACE srovs BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a stove for use in supplying very hot air, e.g., for use in a blast furnace for improving the economy of operation of the blast furnace, and more particularly to improvements in such a stove.

2. Statement of the Prior Art Stack-type blast furnaces are well known in the art of producing cast iron. Such furnaces are usually constructed of a flrebrick lining encased in a steel shell. During operation of a conventional blast furnace, after delivery of raw materials into the furnace, a preheated airblast, produced by the hot blast stove system, is delivered into a ring main surrounding the lower part of the furnace to evenly distribute the airblast for entry into the furnace and up through the raw materials. Such use of hot air has been found to improve the economy of operation of a blast furnace.

The hot blast stoves used for heating the airblast conventionally use stacked brickwork arranged as checkerwork and commonly referred to as checkers" contained in a steel stove casing. Fuel is burned in a combustion chamber of the stove and the combustion gases are passed through the checkers to heat them. The burner is then shut ofi' and an airblast is passed backward through the stove to the blast furnace to provide the requisite hot air for the blast furnace. Because the stove requires heating before it is capable of, in change, heating air for the blast furnace, at least two and normally three or more stoves are provided for each blast furnace to assure a continuous supply of hot air to the blast furnace, one stove being on stream for delivery of hot air while the remaining stove or stoves are off stream for purposes of heating the checkers.

A better understanding of the general overall operation of a blast furnace stove can be obtained by reference to FIG. 1 of the drawings which shows such a stove 11 in combination with a blast furnace 14, although, as stated above, it is to be understood that more than one stove will be provided for each blast furnace. A burner 16 is provided for burning system gas in an elliptical combustion chamber 18 having a laid up refractory wall, separating the combustion chamber from the checker system. The combustion gases from the top of combustion chamber 18 are diverted downward by a reflecting dome 20 through checkers 22 in the checker chamber to heat the checkers. The combustion gases then pass through base manifold 24 and are vented through a chimney 28. After the checkers 22 are heated to the desired or required temperature the burner 16 is shut off and valves 30 and 34 are opened. A compressed air source 32 delivers air through line 26 and through the checkerwork 22 in reverse flow direction through the stove 12. As the air is delivered through checkers 22 it is heated and then travels downward through the combustion chamber 18 and is directed by line 35 into the bustle pipe or ring main 36 of furnace 14 for use in furnace 14. At some predetermined time before the air delivered through line 35 becomes too cool for improving the economy of operation of the blast furnace 14, the stove I2 is shut down by closing valves 34 and 30 and thereby turning off the supply of compressed air from source 32 and diverting the air from source 32 to another newly heated stove. Burner 16 can then be restarted for reheating the checkers 22. Thus, for continuous operation of each blast furnace 14, two or more stoves 12 are provided for alternate use with at least one stove at all times supplying a supply of hot air to the furnace while another stove or other stoves are being heated for subsequent use.

Conventionally the hot combustion gases are normally over 2,000 F. at the top of the combustion chamber at dome 20 and as they pass through the checkers 22 to the bottom of the stove they are cooled to about 700-900 F. As a result, the checkers are heated to a high temperature.

In constructing a hot blast stove for blast furnace use, it has been conventional first to provide a flat circular bottom steel plate which rests on a suitable flat base. A cylindrical steel shell is built and lined with flrebrick from the bottom plate and extends upwardly generally in excess of feet capped by a hemispherical dome. All construction is designed to withstand the maximum pressure encountered during use of the stove. A refractory bottom layer is laid over the bottom plate for protection of the plate from high temperatures. The bottom plate also supports a refractory ring wall, the refractory brickwork forming the combustion chamber, and the checker support structure. The checker support structure is usually an alloy steel structure consisting of footings, columns, crossmembers or beams and checker support bars on which the checkers are stacked. The built-up refractory ring wall made of refractory brick protects the outer steel shell, provides heat retention and assists in holding the checkers against undesirable sideward shifting in the checker zone. The top hemispherical reflecting dome is also lined with brickwork to protect the steel structure and reflect heat into the checkers.

Various zones in the stove are subjected to diflerent temperature conditions during heating of the checkers. For this reason and for reason of economy, the refractory brick linings in blast furnace stoves have been made up of various differing refractory materials correlated with requirements for heat resistance at the various levels of the stove. Further, the alloy steel structure which supports the checkerwork imposes a limitation on the temperature to which the checkers can be heated because heat stresses can cause failures in the alloy steel when heated above 700' to L000 F. Additionally, the steel bottom plate of the stove shell is subjected to severe and nonuniform heat stresses varying from lower temperatures at the periphery of the slab to very high temperatures more centrally. The variance in temperatures and the heat stresses in the bottom seal can cause raising, cracking, cracks and air leaks and ultimate failure in the stove bottom.

There is also a need for improved hot blast stoves for supplying hot air for use in cupolas in the foundry industry as well as supplying large volumes of hot air in aerospace industries.

SUMMARY OF THE INVENTION The present invention provides a stove capable of supplying hot air to a blast furnace or for other uses and the invention overcomes many of the limitations of prior conventional stoves, especially with regard to the cost and time for construction and operation at higher temperatures. For example, much or all of the refractory ring wall normally made of refractory brick is constructed of monolythic refractory concrete varied in refractory properties in accordance with the various heat zones of the stove providing the highest refractory properties at the top section of the stove and lower refractory properties in the bottom section of the stove. The material of lower refractory properties is generally of high structural strength for supporting the weight of the wall above it. The high refractory material nearer the top may or may not have such high structural strength, but high structural strength is not required because it does not have to support as much weight. In a preferred form, a heat exchange system is provided for protecting the checker support structure and even the stove bottom structure can be protected from undue stress by the heat exchange system to prevent failure at high-temperature operation. The stove is thereby capable of heating the checkers to much higher temperatures, especially at lower levels in the stove, to provide a hot blast of air for use in a blast furnace over a longer period of time.

While this invention is susceptible of embodiment in many different forms it is shown in the drawings and will be herein described in detail one form of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the fonn illustrated.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1, as indicated above, is a flow scheme illustration of a combination of stove and blast furnace for showing overall operation of a system which can embody a stove of the present invention;

FIG. 2 is a fragmentary perspective view of the stove bottom, ring wall and checker support structure and showing checkers supported thereon;

FIG. 3 is a composite of horizontal sections through the stove at the checker level on the left and the checker support level on the right;

FIG. 4 is a section along line 44 of FIG. 3 showing the wall structure of the stove;

FIG. 5 is an enlarged side view of one type of support column useful "in the checker support system, but with the outer shell broken away to show underlying structure;

FIG. 6 is a section and view along line 6-6 of FIG. 5;

FIG. 7 is a section and view showing another form of support structure for the checker system, againwith parts of the structure broken away to show underlying structure;

FIG. 8 is a section and view along line 8-8 of FIG. 7; and

FIG. 9 is a section along line 9-9 of FIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENT In view of the above description of the general operation of a blast furnace stovefand turning now to FIG. 2, the bottom wall of the stove is composed of an outer steel baseplate 40 which is supported upon a suitable slab-type support foundation (not shown) and a cylindrical peripheral outer layer 42 upstands from the edges of plate 40 to a hemispherical top terminus or dome as seen in FIG. 1. Flat and angular steel sheets are used to build up an inner liner 44 by securing the sheets in overlapping fashion as best seen in FIG. 4 with machine screws, bolts, or other suitable fastening as at 46 to provide a mortartight joint between the sheets. A layer of block insulation 48 directly backs the steel shell 40. The main structure of the stove shell is an integral layer or ring wall 50 of cast refractory concrete between liner 44 and block insulation 48.

The refractory wall 50 can be made by pouring castable refractory concrete, using first a lower refractory grade concrete near the bottom of the wall and finally progressing to a very high refractory concrete, e.g., containing very high refractory aggregate such as alumina, mullite, silicon carbide or the like, near the top of the wall adjacent dome 2Q. For example, a first or lower refractory concrete can bemade by employing a high quality alumina-silica aggregatein Luminite cement binder, available from Universal Atlas Cement Division, US. Steel Corp., and a separate very high refractory concrete can be made by using a high alumina or mullite aggregate in the binder. Lumiriite cement is a quick-hardening, calciumaluminate cement characterized by its excellent resistance to corrosion and resistance to disintegration by heat. The first concrete is poured in forming the bottom portion of the wall and thereafter the second concrete can be mixed in with the first concrete in increasing proportions as the wall is built up until the top portion of the wall is fonned purely of the second or alumina aggregate concrete.

As a practical matter, usually the construction of the ring wall will involve five or six mixes of concrete, one of low refractory properties, one of high refractory properties and the remainder of varying intermediate refractory properties. For example, there can be used one concrete mix having a straight alumina-silica aggregate and another having a high alumina or mullite aggregate and the remaining mixes being of differing proportions'of the alumina-silica aggregate and high alumina or mullite aggregate are poured in correct order to provide an increasing amount of alumina in the wall as the wall reaches the top or last pour of high alumiria or mullite aggregate concrete. The plurality of mixes are poured on top of the bottom alumina-silica aggregate mix in order of their increasing alumina or mullite aggregate contents, so that after the concretes are set an integral wall is formed having the highest refractory properties or heat resistance at the top, decreasing in refractory properties downwardly toward the bottom. Of course, pressurized or gunnite methods can be used in casting the concretes to form the ring wall in lieu of pouring the concretes.

A wall constructed in this manner can accommodate gases having temperatures as high as 2,500 F. at the top of the wall and can still accommodate such high temperatures as l,0O0-l,200 F. at the bottom of the checkers. Further, the lower refractory material at the bottom of the wall is structurally strong and entirely capable of supporting portions of the wall thereabove while the more highly refractory of the material at the top of the wall, which, in some cases, is not structurally strong, does not have to support much of the weight mass.

Preferably the dome 20 is lined with firebrick or other refractory material supported from the wall gtop edges, although it can be fonned of high refractory concrete. Because of the very high heat resistance of the stove interior provided by the integral refractory wall, the stove is capable of heating the checkers to such high temperatures as 2,0002 ,500 F., very high temperatures compared with previously known conventional stoves.

As shown in FIGS. 2 and 5 through 8, footings 52, e.g., of steel plate, support metal billet columns 54 which can also be of alloy steel. Channel-shaped top plates 56 are secured to the top of billet columns 54 for receiving steel alloy billet beams 58 (see also FIG. 9)which in turn support a network of crossing parallel steel grid bars 60. The checkers 22 are supported on grid bars 60 and are prevented from laterally shifting by ring wall 50. Note that liner 44 is made up of flat sheet, bent at generally square corners to step and keep the liner spaced inwardly and provide adequate space for pouring or otherwise casting wall 50. The square corners are properly spaced to accept conventional sized checkers. A layer of poured refractory concrete 62 is provided over baseplate 40 and covers footings 52 as well as the lower portions of columns 54.

The combustion chamber I8 is formed of an elliptical wall of refractory firebrick 64 held in place by layer 50. The inner layer of firebrick 64a is known as a skin layer while the outer layer 64b is a ring layer. The combustion chamber 18 extends from burner 16 to the top of the checkers 22 so that air from the top end of the combustion chamber is diverted by dome 20 through the checkers 22.

As best shown in FIGS. 7, 8 and 9, each of columns 54 is supported on a separate footing plate 52 which is secured by suitable means such as bolts 70 to bottom plate 40. For cooling, when desired, along each surface ofbillet column 54 there is provided a water cooling tube 72 which weaves back and forth across the face of column 54, extending from the top to bottom of column 54. The water-cooling tubing is normally of copper, stainless steel, or other reasonably heat-resistant material. A sheet metal shield 74, e.g., of stainless steel or the like, is provided over water-cooling tube 72 leaving a dead airgap between sheet 74 and column 54 for insulating purposes. It will be noted that both the water-cooling tubing 72 and the sheet metal shield 74 extend through refractory concrete layer 62 to the footing plate 52 so that column 54 is cooled all the way down to the footing 52. Further, the tubing adjacent footing 52 assists in cooling the footing. Thus, the entire structure of column 54, tubing 72 and shield 74 is completed before pouring bottom refractory concrete layer 62.

For cooling purposes, water-cooling tubing 76 can also be provided on billet beams 58, weaving along the faces of beams 58 in generally the same manner as they weave down the billet columns 54, except that the tubing is provided only on the side and bottom faces and is absent in those areas contacted by channel-shaped receivers 56. A sheet metal shield 78 is also provided over the tubing 76 on beams 58.

Prior to pouring layer 62, cooling water ducts 80, if used, are laid or welded against the upper surface of bottom plate 40. In use of the stove, i.e., during the heating cycle, water or other heat exchange fluid is circulated through tubing 72, tubing 76 and ducts 80 to cool all steel members within the support system structure.

Although rolled steel billets are normally of generally square or rectangular cross section with rounded corners, other forms can be used. For example, turning now to FIGS. 5 and 6, a form of circular cross section column tubing and heat shield is shown. Accordingly, columns 54a are round billet bars and water-cooling tubing 72a is of spiral form conforming with the outer surface of column 540. The heat shield 74a is tubular and closely spaced outwardly from tubing 72a to again provide a dead air space between shield 74a and column 540. The lower end of shield 74a is received in and secured to a circular flange 82 which in turn is secured to the footing plate 52.

During operation of the stove, the support structure for checkers 22 can be maintained at a low nondamaging temperature while much hotter combustion gases are used in the stove to heat the checkers to much higher temperatures because of the removal of excessive heat from the steel members of the checker support structure by heat exchange fluid circulated through the heat exchange tubes and ducts. Most important, however, the alloy steel support structure is protected by cooling against failure. Further, because concrete is used for the refractory wall, a stronger wall structure can be provided using stronger lower refractory concrete at the bottom and the heat resistance of the wall can be adjusted by adjusting the composition of the refractory concrete to accommodate the various levels of the stove which are subjected to different temperatures so that very high quality refractory concrete can be used toward the top of the wall where the structural strength requirements are not so great.

As another advantage, the use of the poured refractory concrete permits construction of a facility at a far lower cost than previously involved, e.g., as much as 20 to 25 percent below the cost of a refractory brickwork ring wall. Additionally, where time out of service is a factor in awaiting construction of a new stove, the present invention can reduce construction time by as much as to 25 percent.

Although the operation of the stove of the present invention will be apparent from the foregoing description, in the embodiment shown the burner 16 can be larger than conventionally used and produces combustion gases having a temperature as high as 2,500 F. as they exit combustion chamber 18 and reflect from dome 20. After passage through checkers 22 the gases directed from chamber 24 through chimney 28 are also much higher than normal and can be operated in the range of about l,0O0 to l,200 F., resulting in the checkers 22 being heated to higher temperatures and enabling them to heat larger quantities of air or to heat air to higher temperatures for use in blast furnace 14. The stove of the present invention thereby has a much improved ability in increasing the economics of operation of a blast furnace, while still overcoming failures previously believed to be inherent in such hightemperature stove operation.

lclaim:

ll. In a stove for supplying a hot airblast in which checkers are contained within an elongate upstanding shell system, the improvement wherein said shell comprises a monolythic refractory concrete wall of varying heat resistance with the thermal resistivity of the concrete being greatest at the top of the wall and varying down to lesser refractory properties and greater structural strength at the bottom of the wall.

2. The stove of claim 1 in which a burner is employed in a combustion chamber for heating the checkers by passing combustion gases through the checkers from an inlet to an outlet of the checkers and said concrete is resistant to a temperature of from about 2,200 to about 2,500 F. at the checkers inlet and resistant to temperatures of about l,000 to about 1,200" F. at the checkers outlet.

3. The device of claim ll wherein said shell means includes overlapping steel plate means lining the interior of the cast refractory concrete and including a plurality of steel plates with mortartight joints between the plates.

4. The stove of claim 3 wherein said lining means comprises a form for casting the refractory concrete.

S. The stove of claim 1 including a support system for supporting the checkers exposed to heating gases leaving said checkers and including alloy steel support members and means for cooling said support members while the checkers are being heated.

6. in a stove for supplying a hot airblast in which checkers are contained within an elongate upstanding shell system, the improvement wherein said shell comprises a monolythic refractory concrete wall of varying heat resistance, said concrete wall consisting essentially of high refractory aggregate having refractory properties substantially in the range of those of alumina, mullite and silicon carbide at the inlet of the checkers at the top of the wall, alumina-silica aggregate at the outlet of the checkers at the bottom of the wall and a gradually increasing proportion of alumina in alumina-silica aggregate from the bottom to the top of the wall.

7. The stove of claim 6 wherein the aggregate at the inlet of the checkers at the top of the wall essentially consists of [00 percent alumina.

8. In a stove for supplying a hot airblast in which checkers are supported by a support system including alloy steel members in the form of columns, the improvement comprising means for cooling said support members while the checkers are being heated including heat exchange means for passing a heat exchange medium in heat-receiving proximity to the members and shield means mounted exteriorly of the heat exchange means for creating an insulating dead air space therebetween.

9. The stove of claim 8 wherein said shield means comprises a metal sheet surrounding the member.

10. in a stove for supplying hot airblast in which checkers are supported by a support system including support members supported by a steel baseplate, the improvement comprising means for cooling said baseplate.

11. The device of claim 10 including a refractory concrete layer over said baseplate and wherein the cooling means comprises fluid ducts imbedded within the concrete in heat receiving proximity to the baseplate.

12. The device of claim 11 wherein said tube means comprises a series of parallel tubes for conducting water adjacent the baseplate surface.

13. The stove of claim 10 including means for cooling said support members while the checkers are being heated.

14. The stove of claim 13 wherein said support members comprise columns and the cooling means comprises heat exchange means for passing a heat exchange medium in heatreceiving proximity to the columns.

15. The device of claim 14 wherein said heat exchange means comprises tube means laid against the billets for conducting water.

16. The device of claim 15 wherein said columns are square columns and the heat exchange tubes are in the general form of a compacted sine wave along each face of the billet.

17. The stove of claim 15 wherein said columns are rounds and said tube comprises a spiral around the column at the surface thereof.

18. The device of claim 13 wherein said support members include billet beams and cooling means therefor, comprising heat exchange means for passing a heat exchange medium in heabreceiving proximity to the beams.

19. The stove of claim 18 wherein the heat exchange means comprises tube means for conducting water along the surface of the faces of the beams.

20. In a stove for supplying a hot airblast in which checkers are supported by a support system including substantially horizontal billet beam means for supporting said checkers, the improvement comprising means for cooling said billet beam means while the checkers are being heated including tube means for conducting water along the surface of said beam means to receive heat therefrom and shield means under said tube means creating an insulating dead air space between the shield means and beam means. 

1. In a stove for supplying a hot airblast in which checkers are contained within an elongate upstanding shell system, the improvement wherein said shell comprises a monolythic refractory concrete wall of varying heat resistance with the thermal resistivity of the concrete being greatest at the top of the wall and varying down to lesser refractory properties and greater structural strength at the bottom of the wall.
 2. The stove of claim 1 in which a burner is employed in a combustion chamber for heating the checkers by passing combustion gases through the checkers from an inlet to an outlet of the checkers and said concrete is resistant to a temperature of from about 2,200* to about 2,500* F. at the checkers inlet and resistant to temperatures of about 1,000* to about 1,200* F. at the checkers outlet.
 3. The device of claim 1 wherein said shell means includes overlapping steel plate means lining the interior of the cast refractory concrete and including a plurality of steel plates with mortartight joints between the plates.
 4. The stove of claim 3 wherein said lining means comprises a form for casting the refractory concrete.
 5. The stove of claim 1 including a support system for supporting the checkers exposed to heating gases leaving said checkers and including alloy steel support members and means for cooling said support members while the checkers are being heated.
 6. In a stove for supplying a hot airblast in which checkers are contained within an elongate upstanding shell system, the improvement wherein said shell comprises a monolythic refractory concrete wall of varying heat resistance, said concrete wall consisting essentially of high refractory aggregate having refractory properties substantially in the range of those of alumina, mullite and silicon carbide at the inlet of the checkers at the top of the wall, alumina-silica aggregate at the outlet of the checkers at the bottom of the wall and a gradually increasing proportion of alumina in alumina-silica aggregate from the bottom to the top of the wall.
 7. The stove of claim 6 wherein the aggregate at the inlet of the checkers at the top of the wall essentially consists of 100 percent alumina.
 8. In a stove for supplying a hot airblast in which checkers are supported by a support system including alloy steel members in the form of columns, the improvement comprising means for cooling said support members while the checkers are being heated including heat exchange means for passing a heat exchange medium in heat-receiving proximity to the members and shield means mounted exteriorly of the heat exchange means for creating an insulating dead air space therebetween.
 9. The stove of claim 8 wherein said shield means comprises a metal sheet surrounding the member.
 10. In a stove for supplying hot airblast in which checkers are supported by a support system including support members supported by a steel baseplate, the improvement comprising means for cooling said baseplate.
 11. The device of claim 10 including a refractory concrete layer over said baseplate and wherein the cooling means comprises fluid ducts imbedded within the concrete in heat receiving proximity to the baseplate.
 12. The device of claim 11 wherein said tube means comprises a series of parallel tubes for conducting water adjacent the baseplate surface.
 13. The stove of claim 10 including means for cooling said support members while the checkers are being heated.
 14. The stove of claim 13 wherein said support members comprise columns and the cooling means comprises heat exchange means for passing a heat exchange medium in heat-receiving proximity to the columns.
 15. The device of claim 14 wherein said heat exchange means comprises tube means laid against the billets for conducting water.
 16. The device of claim 15 wherein said columns are square columns and the heat exchange tubes are in the general form of a compacted sine wave along each face of the billet.
 17. The stove of claim 15 wherein said columns are rounds and said tube comprises a spiral around the column at the surface thereof.
 18. The device of claim 13 wherein said support members include billet beams and cooling means therefor, comprising heat exchange means for passing a heat exchange medium in heat-receiving proximity to the beams.
 19. The stove of claim 18 wherein the heat exchange means comprises tube means for conducting water along the surface of the faces of the beams.
 20. In a stove for supplying a hot airblast in which checkers are supported by a support system including substantially horizontal billet beam means for supporting said checkers, the improvement comprising means for cooling said billet beam means while the checkers are being heated including tube means for conducting water along the surface of said beam means to receive heat therefrom and shield means under said tube means creating an insulating dead air space between the shield means and beam means. 